Partial update of r packages possible?

Hello

I'm on Ubuntu 8.04 but I added in my source list some local mirror so I 
have possibility to upgrade to R 2.8. However, it seems that there is a 
dependency problem, (should install some liblapack libraries). This is 
not the problem, I can keep R 2.7.

However, even if I'm not able to install R 2.8, the other packages:
-r-base-html
-r-base-doc
-r-doc-info
-r-doc-html
-r-doc-pdf
-some packages: kernsmooth, mgcv,

are still suggested to be installed. Will that not create some conflict 
with package builded on R 2.8? Won't I have documentation for R 2.8 
running on R 2.7?

Thanks!

Matthieu